1. Field of the Invention
The present invention relates generally to spread spectrum communication systems and more specifically to a code division multiple access (CDMA) communication receiver having an array of antennas whose directivity pattern is adaptively controlled.
2. Description of the Related Art
For CDMA communication receivers, it is known to use an adaptive array of antennas for receiving user signals. Each of the received user signals is separated into multipath components, which are supplied respectively to adaptive processing units so that each unit receives a set of multipath components of same arrival time. In each processing unit, the input signals are respectively multiplied with weight coefficients and summed together to produce a weighted sum signal. This signal is despread with a chip sequence and demodulated. The demodulated signals from the processing units are combined in an adder and a threshold decision is performed on the output of the adder to produce a symbol output. Each processing unit detects a decision error of the symbol output and produces the weight coefficient by detecting correlations between the set of multipath components and the decision error.
However, since the adaptive processing units are provided in number corresponding to the number of multipath components, and each unit performs weighting and summing operations and updating the weight coefficients, implementation of the prior art system suffers from hardware complexity. Additionally, difficulty is encountered for the prior art antenna array to create a distinct directivity pattern when the signals received by the antennas contain numerous multipath components, particularly when they contain weak components, due to decreased reliability of the decision errors.